In electrical pulsed power applications, inductors are needed for pulse shaping and/or energy storage. In the past helical jelly roll inductors have been used. Helical jelly roll inductors are generally high current inductors constructed by winding long copper strips around an insulating cylinder then overlaying the windings with a layer of fiberglass to withstand internal magnetic pressure. U.S. Pat. No. 5,912,610 entitled “High Energy Inductor”, which is hereby incorporated by reference, describes this type of helical jelly roll inductor in detail.
A desirable feature presented by the high energy inductor of the '610 patent is that it is designed to be of sufficient strength to withstand the typically destructive magnetic field forces that result from high pulse current flow while still presenting an inductor of smaller weight and volume. In brief, high energy pulses, which involve high currents, generate such high magnetic field forces that an inductor can literally explode unless fabricated in a fashion to provide high mechanical strength. Typically, this requires that the inductor be of substantial weight and volume. However, the high energy inductor of the '610 patent was able to limit the weight and volume of the inductor by imposing and maintaining a predetermined level of tensile stress upon the length of the conductor of the inductor.
Thus, while the problems of weight and volume of inductors for electrical pulsed power applications have been addressed in one form, the issue of stray magnetic fields remains a problem. Specifically, helical jelly roll inductors, such as the one described in the '610 patent, have been shown to emit strong magnetic fields that typically exceed MIL-SPEC acceptable limits. These fields can be very harmful to electronic equipment in an armored vehicle or on a ship. Further, large stray magnetic fields create a presence that may be detectable by enemy sensors.
In one attempt to solve the stray field problem, an inductor was created by assembling several helical jelly roll inductor segments into a toroidal geometry (“segmented toroid”) by attaching the segments to a central bucking cylinder. The bucking cylinder was designed to resist the implosive forces of the inductor. This “segmented toroid” exhibited significantly lower stray fields but was quite bulky.